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ApplicationStatePersistenceStrategy.java
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/
ApplicationStatePersistenceStrategy.java
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// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements. See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership. The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License. You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied. See the License for the
// specific language governing permissions and limitations
// under the License.
package org.apache.tapestry5.services;
/**
* Used by {@link ApplicationStateManager} to manage a specific kind of Session State Object (SSO)
* persistence. The
* strategy is responsible for managing SSO instances within its domain.
* <p>
* <em>NOTE: The term "Application" here is a hold-over from Tapestry 5.0, which used the @ApplicationState
* (deprecated and deleted) annotation, and called them "ASOs" (Application State Objects). This service
* would be better named "SessionStatePersistenceStrategy" (but renaming it would cause backwards
* compatibility issues).</em>
*
* @see org.apache.tapestry5.services.ApplicationStatePersistenceStrategySource
*/
public interface ApplicationStatePersistenceStrategy
{
/**
* Gets the SSO from the domain. If the SSO does not already exist, it is created and stored, then returned.
*/
<T> T get(Class<T> ssoClass, ApplicationStateCreator<T> creator);
/**
* Stores a new SSO, possibly replacing the existing one.
*
* @param <T>
* @param ssoClass
* @param sso instance to store, or null to delete existing
*/
<T> void set(Class<T> ssoClass, T sso);
/**
* Returns true if the SSO already exists, false if null.
*/
<T> boolean exists(Class<T> ssoClass);
/**
* Returns the SSO if it exists or null.
*/
default <T> T getIfExists(Class<T> ssoClass) {
return exists(ssoClass) ? get(ssoClass, () -> null) : null;
}
}